The invention concerns a method for fixation of anchoring bolts in boreholes.
It is common practice to use unsaturated polyester resins and polyurethanes as reactive resin mass for fixation of anchoring bolts in boreholes. To these ends, the two components used for polyurethane formation, i.e. polyisocyanate and polyol, are contained in two separate chambers of one cartridge made either from plastic foil or an extruded brittle mass (we refer to DE-PS 26 41 776). By introducing the bolt with rotary motion into the boreholes, both chambers are destroyed and both components are mixed, so that they react with each other to form polyurethane. According to DE-AS 12 05 038 and DE-AS 17 84 458, the polyurethane resin takes two hours for assuming the consistence of a jelly, and 5 to 6 hours for solidifcation. For practical reasons, however, much shorter gelatination and hardening times are required, since until gelatination the anchoring bolt needs to be secured in upwardly directed boreholes against falling-out, and since the whole system needs to develop carrying capacity as soon as possible, particularly for tunnelling and mining.
DE-AS 27 05 751 describes the system which avoids this disadvantage, with polyols containing tertiary amino groups being used as hydroxyl components, which at the same time exert catalytic effects, so that gelatination and hardening times of less than one minute are achieved. According to claim 3 of this disclosure, however, water addition is limited to 0.5% by weight relative to the polyol. If more water is added, e.g. from outside by moist boreholes, the blend foams up to such an extent that the hardened foam produced will not stand serious tractive efforts.